Feature Fourier, One one man,Man, Several several Lives lives Bernard MaureyMaurey (Sorbonne (Sorbonne Université, Université, Paris, Paris, France) France) Fourier was born 250 years ago, twenty-one years before the run by monks. After finishing school, at the age of 19, he ap- French Revolution in 1789. The events of those troubled times plied for admittance to the entrance examination to the ar- turned his life into an adventure novel: the Revolution with its tillery, which was curtly refused him. “Not being noble” , it mortal dangers; Bonaparte’s expedition to Egypt with its dis- was impossible for Fourier to become an artillery officer. So coveries; later a political career as prefect of Isère at Greno- he turned to the religious orders and became a novice at the ble, where Fourier wrote the first versions of the Théorie an- Benedictine Fleury Abbey in Saint-Benoît-sur-Loire. He lived alytique de la chaleur, when he was not busy with the con- there for two years, from 1787 to 1789, and could have be- struction of the road from Grenoble to Turin or the drainage come Father Fourier, but the French Revolution broke out and of marshland at Bourgoin; and finally, his academic role at the constituent Assemblée nationale issued decrees suspend- the very heart of the Parisian scientific community during the ing the pronunciation of religious vows just before Fourier years 1820–1830. While relating a variety of aspects which would pronounce his own in November 1789. Early in 1790, are not all of scientific concern, we shall, of course, dedi- he returned to his former school in Auxerre, this time as a cate an important space to the theory of heat, Fourier’s ma- teacher. It was called “Collège National–École Militaire” at jor work, as well as to the Fourier series, which are a crucial that time. He stayed there for four years, taught different sub- element of his mathematics. jects such as history, philosophy, eloquence and also mathe- matics, and became a “civil servant teacher”. Some books about Fourier Initially reserved towards the French Revolution, Fourier engaged in the Comité de surveillance of Auxerre at the be- Numerous authors have written about Fourier, especially from ginning of ’93 and even became its president in June ’94. He the second half of the 20th century onwards, when several witnessed violent scenes of desecration of churches during the new works were published. Jean Dhombres and Jean-Bernard wave of dechristianising of 93–94, although we do not know Robert have done a colossal work [D–R] , which I did not hes- what his feelings about it were. From September ’93 onwards, itate to exploit, although often at the price of regrettable sim- the Comité d’Auxerre found itself in charge of executing the plifications. A new work, under the direction of Dhombres, is decisions of Maximilien de Robespierre and the Comité de to appear this year [Fo-R]; it aims at a broader public, contains Salut Public. Fourier, being rather moderate, might have been a great number of illustrations and as yet unpublished archive jeopardised by his lack of zeal in supporting the head cut- material. Ivor Grattan-Guinness was the first to publish, in ters. Victor Cousin, his successor at the Académie française his 1972 book [GraF], the content of the essay Sur la prop- in 1831, reported in the Notes additionnelles à l’éloge de agation de la chaleur presented by Fourier at the Académie M. Fourier – years after the events – that Fourier had delib- des Sciences in December 1807. Umberto Bottazzini [Bott] erately spoiled the arrest, in the town of Tonnerre, of a man dedicated two sections1 to the study of the heat problem in sentenced to the scaffold.3 Nevertheless, Fourier signed a cer- the years 1800–1830. Another book I am going to refer to tain number of arrest warrants in the context of his compe- is the one by Jean-Pierre Kahane and Pierre Gilles Lemarié- tence in the Comité d’Auxerre. One event was to have led to Rieusset [K–L], the first part of which, written by Kahane, his imprisonment: the “affaire d’Orléans”, which is reported presents a history of Fourier series. The treatise on harmonic in great detail by Herivel.4 analysis by Thomas Körner [Körn] masterly sets out the Early in October ’93, Ichon, a member of the Convention, mathematics attached to the name of Fourier. It also contains was despatched to collect weapons, equipment and horses in two small chapters on Fourier’s life2, which are based mainly the Yonne and six surrounding départements, preparatory to on the very informative book by John Herivel [Heri]. certain operations in the Vendée. With this aim, he named six citizens of Auxerre – among them Fourier – for a one-month 1 The Revolution, the Egypt campaign mission in Orléans from mid-October onwards. The city was troubled by the conflicts between sans-culottes and bourgeois. Jean-Baptiste Joseph Fourier was born on 21 March 1768 Laplanche, also a member of the Convention, had been sent in Auxerre. The baptism certificate bears Jean-Joseph as his there from Paris at the beginning of September. He first took first name. He was born into a family of craftsmen in social revolutionary measures supposed to satisfy the sans-culottes, ascension: his father, a tailor, had about ten employees. At the but then he did not resist the pressure from the richer classes age of ten, Jean-Joseph was orphaned and the clergy of Aux- and clashed with the leaders of the sans-culottes. Fourier op- erre took care of him. There was a remote – and uncertain posed himself to Laplanche and, clearly exceeding the scope – family relationship with a beatified priest, so the abandon- of his mission, supported the “left wing”, as we would call it ment of the boy was out of the question. He received a good today. As a result, Laplanche and the authorities of Orléans education at the École Royale Militaire d’Auxerre , which was requested Fourier’s recall to Auxerre and denounced his be- 1 [Bott, 2.3, 2.4] 3 [D–R, ch. III, p. 94] 2 [Körn, part VI, ch. 92 and 93] 4 [Heri, 2.2] 8 EMS Newsletter September 2019 Feature haviour. Their complaint was transmitted to Paris. A decree Yonne (reproduced by Dhombres and Robert7), under the cir- from Paris relieved Fourier of all his duties on 29 October ’93: cumstances mentioned above, when Fourier tried to justify his “The Commission conferred [. ] to the citizen Fournier [sic] behaviour in the years ’93–’94, his integrity being questioned. is revoked; he is no longer authorised to receive such Com- As an outstanding student of the École Normale, he at- missions”, and he was not permitted to carry out any more tracted the attention of Gaspard Monge, he attended lectures public functions. Ichon, who was responsible for Fourier’s of Pierre-Simon Laplace and of the eminent Joseph-Louis La- dispatch to Orléans, felt part of the blame reflecting on him; in grange, “the first among Europe’s scholars”, as Fourier wrote his fury, he issued an arrest warrant against Fourier, who for- in his Notes sur l’École Normale.8 Laplace, an acknowledged tunately had not returned to town yet. As things had calmed scientist under the Ancien Régime, had to seclude himself down a bit by his return to Auxerre, he was left in peace. during the Terreur; in ’95, he reappeared on the scene and Meanwhile, the Orléans affair ended up reappearing in Paris. quickly became very influential. Fourier mentioned in his With Robespierre fighting to his left as well as to his right, the Notes that he also attended lectures on physics by René-Just agitators from Orléans were targeted, and so was Fourier. On Haüy, on chemistry by Claude-Louis Berthollet as well as 19 June ’94, the Comité de Sûreté Générale ordered his arrest the lectures by the – very old – naturalist Louis Jean-Marie (it was the very June the “Grande Terreur” law was adopted). d’Aubenton (I am citing only the most well known). When We know today [Fo-R] that Fourier was not imprisoned, he the École Normale was closed, Fourier became a teacher at benefitted from privileged treatment and was put under house the École Polytechnique (which we are going to refer to sim- arrest on 4 July at his home in Auxerre. Robespierre fell at the ply as “the École” in the following; before September ’95 end of July and Fourier was “freed” on 11 August. it was called École Centrale des Travaux Publics). Recom- At the end of ’94, Fourier was selected as one of the young mended by Monge, he became substitut at the École at the teachers to be trained at the newly established École Nor- end of May ’95 – his mission consisted of supervising the male, the “École Normale de l’an III”. The institution lasted students’ works –, then assistant teacher in October ’95. For only one semester, from January to June ’95. Fourier was a over two years, he deeply committed himself to his duties as distinguished student, but because of political changes, his a mathematics teacher. former participation in the Jacobin committee got him into One can get an impression of the lectures held by Fourier trouble. In times of the Thermidorian Reaction, a hunt for from 1796 to 1797 from the notes taken by students,9 which “terrorists” was taking place. The new authorities in Auxerre are kept at the Institut de France and at the École des Ponts wanted Fourier to be expelled from the École Normale; they et Chaussées.10 These lectures were not based on the manuals reproached him with his past in an address to the Convention from the 18th century (like the treatise by Étienne Bézout), but Nationale:5 rather inspired by Lagrange and Laplace’s lectures given at the École Normale; also the geometric spirit of Monge is dis- We, the Representatives, shudder when we consider that the cernible.